4L80e delayed shift into D, stalls engine

[stutaeng]

Hi guys, I've noticed my 00 K3500 wants to stall when I leave my driveway. I've let it warm up to closed loop and my scanner reads around 190F, but no difference.

So I put into R or D and it wants to stall and there's a slight delay. Almost feels like a manual transmission with clutch engagement. If I put it into D on a light incline in my backyard I can replicate the issue. Feels like it's in neutral. If I give slight gas below 1,000 RPM it wants to stall, then it catches and wants to roll forward, with a drop in engine RPM.

I've driven about 1 mile and at a stop light it has stalled, not always. After that it doesn't do it again. TPS and MAF seem to be reporting accurately, as well as ETC. Basically everything seems right on the engine side. No codes. Swapped TPS and IAC valve with known good ones without change.

I think it's tranmission causing this. Truck has 206k miles. I bought it about 2 years ago, but haven't driven it much. Haven't touched the tranmission. It otherwise seems to shift great on all gears.

Only thing I've done is replace all 4 O2 sensors and did the MPFI upgrade. It's all stock as far as I know.

What should I do?

Drop the pan and do fluid change? Or get line pressure gauge set to look a line pressure? Anything else to look into?

 

[Erik the Awful]

Check your transmission fluid level with the engine running. It sounds like it's low, and if sitting on an incline gets it to act up, that's likely part of your problem. The stalling is probably a second problem.

 

[Supercharged111]

Could be the torque converter. My 1500 has always had this thing since I built the 4L80 where, if it's winter, the motor gets lugged down when you take off the first time or 2. It doesn't die when you put it in gear though. When you take off it feels like the converter locks but I think that's impossible in 1st. I think there's a sprag that can fail and cause what you describe inside the converter.

 

[stutaeng]

Um, checked ATF level and on R it looks in the normal range but in D it looks overfilled?

I am seeing my coolant reservoir tank slowly drying up, in the little driving I'm doing on the truck. I put a new radiator also when I just bought it. The plastic top part had a crack and the PO put some JB weld on it.

I see a little aeration on the dipstick. I don't think that's normal, us it?

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First photo is in D
Second photo is in R

 

[stutaeng]

I was also thinking TC locking up causing the stall, but that only occurs in 4th gear?

I barely have knowledge on how that thing works...

 

[90 Silverado]

On the GM TH 125C trans,(FWD) car would stall if the Lockup solenoid would fail, remedy would be pulling the plug on the side of trans to turn off the Lockup.

Don't know if your trans has a fuse or not
for lockup , from watching Presision Transmission on YouTube, on those trans theyhave everything on the valve body
which means pulling the pan, also those o rings on the shaft of the trans that go into the covertor get brittle and the pump doesn't function properly.

Best to find a someone with a trans code reader to find out the real problem.

Doug in P.R.

 

[andy396]

There’s a scenario that can cause the TCC to engage at idle.

Here’s a link to some of my previous comments about the topic.

https://www.gmt400.com/threads/torque-converter-issues.50294/#post-1116746

 

[stutaeng]

Thank you guys. Looks like I'll be doing more reading. The weird thing is that mine only does it cold. I don't know if idling in P where coolant temperature is up to 190F brings up tranmission fluid temperature up to operating temperature. Or if actually driving it down the road does.

I don't have a transmission temperature gauge.

In any case, not sure why after warming up the issue goes away. I think dropping the pan and changing fluid would be the first step?

Also inspecting the ATF cooling lines. I do have the trans.auxiliary cooler. Saw it today after looking around. Didn't even know I had that.

 

[Supercharged111]

My issue is also only when cold. I figure metal expanding when warm has something to do with it.

 

[stutaeng]

My issue is also only when cold. I figure metal expanding when warm has something to do with it.

Yeah, that make sense. Or maybe an oring not sealing well when it's cold?

I haven't messed with the 4x4 transfer case. Not sure if that would cause anything like that? Maybe at least check the fluid level. Don't have a remote idea how that's done. Need to look it up!

I think I'll keep running it as is, LOL